STUDIO DELL'INFLUENZA 'TROFICA' DEL MOTONEURONE SULLE GLICOPROTEINE DI MUSCOLI TONICI E FASICI: I. NANA ED ESOSAMINE

The basis for this investigation was the hypothesis that quantitative or qualitative differences of sialo glycoproteins, which are important constituents of all cell membranes, might underlie different membrane properties of slow and fast, normal and denervated muscles. The results showed that the concentration of N acetyl neuraminic acid (NANA) in the fat free dry residue is 1.8 times higher in soleus than in gastrocnemius; the concentration of glycoprotein bound hexosamines is 1.4 times higher in soleus than in gastrocnemius. Following denervation, the concentration of glycoprotein bound carbohydrates increases in both muscles, but the increase is more pronounced in gastrocnemius. For better understanding of the modifications following denervation, it was necessary to assay the total content of glycoprotein bound carbohydrates per muscle in controls and denervated animals. Following denervation the total content of glycoprotein bound NANA increases considerably only in gastrocnemius; it stays steady in denervated soleus for at least fifteen days of denervation. The total content of hexosamines does not change significantly, either in gastrocnemius or in soleus. These results suggest that glycoprotein metabolism is under neural influence in the fast but not in the slow muscle. The biological significance of these observations is only speculative; it is interesting that following denervation, glycoprotein metabolism of gastrocnemius becomes similar to that of normal and denervated soleus.